Centralized traffic controlling system for railroads



s. N. WIGHT 2,368,957

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Feb. 6, 1945.

Filed July 22, 1941 2 Sheets-Sheet 1 EM W m mw v Tina 3 Q 1, JUOQ a m own U, Tm

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Patented Feb. 6, 1945 'UNITED STATES PATENT OFFICE,

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAJLROADS Sedgwick N. Wight, RochestenN. Y., assignorto General. Railway'Signal Company, Rochester,-

Application July-22, 1941, Serial No. 403,526-

12 Claims.

The present invention relates to centralized traffic controlling systems of the code type and more particularly to the indication portion of such systems for transmitting indications from field stations to a central office.

In centralized trafiic control systems of the code type an operator or dispatcher at aicentral office controls the track switches and signals at various points on a railway system extending as much as one hundred mile in one direction from a central ofiice, and in order for the operator to control such switches and signals he must; of course, be informed as to the locations of the trains, the positions of switches, and the indicating conditions of signals. In a system of the. type just referred to, a considerable amount oftime is required for the transmission of a singlecontrol code from the ofiice to a field station and also for the transmission of an indication code from the field station to the oflice, and in the larger systems, in view of the large number of indications required, it is quite common for the system if' a track switch does not assume a position in correspondence with the position of its-control relay, within a predetermined period of time after such control relay has been operated, this period of time being long enough to allow the slowest switchto operate from one position to another, an out-of-correspondence indication code will be transmitted to the ofi'ice to light an out-of-correspondce indication lamp associated with that switch machine lever. With this out-of-correspondence indication lamp lighted, the operator will know that the switch assumes a different position than does the switch control lever. If, on the other hand, the out-of-correspondence indication lamp is not-lighted, the operator may rely upon the position of the switch control lever as an indication'of the positionassumed by the tion lamp is also true of the signal control lever to get overloaded, that is, more codes are required to be transmitted in a particular period of time than the system can handle, which means that trains will be delayed by reason of the improper indications of signals, the locations of trains, and the positions of switches.

In accordance with the present'invention it is proposed to take advantage of the positions of switch levers and signallevers to'inform the operator as to the positions and conditions of such switches and signals. It is, of course, understood that in the great majority of instances the switch will immediately follow a change in the position er code is transmitted to the field.' This, for ini stance, might be due to an obstruction'between the switch points or by reason of the presence of a train on the approach section .to the track switch which would prevent its operation. Similarly, a signal will not necessarily assume the clear condition in response to the transmission of a signal-clear coda-because the track section directly in advance of such signal may be occupied by a. train. In accordance with the present invention'it is proposed to provide means whereby if an individual out-of-correspondence indication lamp is provided for such signal control lever, as may be done, if desired.

Another object of the present invention: resides in the provision of a single out-of-correspondence indication lamp for indicating when anyone of a plurality of signals or the track switchat a par-'- ticular field station is out of correspondence with its control relay, if desired.

Another object of the present invention resides in the provision of means .for extinguishing an out-of-correspondence indication lamp local to such lamp when the associated control lever has been operated to a new position.

Another object of the presentinvention resides in the provision of means for restoring the out-ofcorrespondence code transmitting means at a field station to its normal-condition after it has manifested an out-ofcorrespondence condition,

such restoration being accomplished by the transmission of a new control code to that field station. 1

Other objects, purposes and characteristic features of the present invention 'will'in part be pointed out hereinafter and in part be obvious spondence condition exists between any one of four signals and their respective control relays or between the associated track switch and its control relay.

In order to simplify the illustration and description of the present invention, it has been shown applied to the, code type centralized trafiic controlling system illustrated in the patent to Judge et al., No. 2,082,544, as modified in the patent to Hailes et al., No. 2,229,736. It should, however, be understood that the invention may also be applied to a centralized trafiic controlling.

system of the two-line wire code type such as.

illustrated in the application oi Hailes et al., Ser. No. 197,404, filed March 22, 1938, which has been issued as Patent No. 2,259,561, dated October 21, 1941, as well as to the four=line wire type code system illustrated in the patents to Judge et al., No, 2,082,544, and Hailes et al., No. 2,229,136, above referred to.

Referring to Fig.1 of the drawings attention is directed to the. fact that, those: portions of the. drawings shown in, light lines comprise, "1101? tionsof Fig. land: Fig. 3A of the. patent .to'Hailes et. al.,. No. 2,229,736; whereas, they wires and partsshowninheavy lines are those features of the system that must be. added to comprise the. system of thepresent. invention. Also, re.-

to each other while others are at'considerable distances. That apparatus located within a limited area determined by the convenience and economy with which the apparatus may be interconnected by direct control wires, is conveniently termed a field station. A code type selective communication system then provided to interconnect the control ofiice with the'several outlying field stations for the transmission of controls and indications to and from these field stations.

ferring to Fig; 2A and Fig. 2B of the drawings it should be. understood that the apparatus. il-. lustrated in Fig. 2A in light lines. corresponds. to. a. portion of the apparatus illustrated in Fig 1 of the. Hailes etal. patent andthat the. apparatus. illustrated in light. lines in Fig. 2B. of the drawings. corresponds to. all of the apparatus illustrated in-Fig; 3B of this same patent to Hailes et al., No.. 2,229,736.; whereas, the portions illustrated in heavy lines comprise a modifled form of the present invention superimposed thereon. In. view of the-fact thatthe communi.. cationsystem to which the present invention is applied is. fully described in the patents to. Judge et al. and Hailes et a1. only. a brief discussion of this portion of the apparatus will be given so. that'the greater portion of the specification may be. used to describe the features of the present invention,

In acentralizedtraflic controlling system of the type contemplated by this invention, the switches and signals at various points along a railroad are placed under the control of an.operator'in a centralcontroloffice', in such a way that. the operator may at will change the position of the switches. subject to automatic ap-- proach and detector locking circuits which prevent unsafe. operation of any switch, and such away that the. operator may at will hold at. stop any of. thesignals or allow them to cleardependent. upon the position of the associated switches: and the location of trains within certain track sections in advance, so that the sig n-als indicate proceed only when it issafe for the passage of trafiic. Also, the system pro vides meansxwhereby indications are. displayed in the control ofiice to. inform the operator of This code selective type communication system requires only a small number of line wires to establish communication between the control ofliceiand a large, number of field stations with means providing for the transmission of a large number of controls and indications for each of thefieldstations. The system illustrated is of the two circuit type having a control line circuit and an indication line circuit, which circuits are made up by theprovisionoi at, leastthree. line wires, one control line wire. onev indication line wire; and a common return line. wire. In the illustrations, howevenzthe controlv line is provided with an individual return'line, and'simi larly the; indication line isprovided. with an individual return line. However, if desired, a single, circuit. two-wire communication system suchas. illustrated and- ,described in the patent toxI-Iailes et. al., Patent No. 2,259,561, dated. 00.- tober- 21', 1941, may, if desired, be employed in practicing the present invention.

Communication is established between the control oflice andzthe. several field stations by the transmission of suitable codes, which cause theselector. type apparatus at each'locationrto operate step-by-stepthrough cycles of operation. The. system upon which the present ine vention is superimposed is of the. station-select tive coded duplex type, wherein controls. and/or indications may be transmitted during any particul-ar operating cycle of the system.

For the transmissionof. controls, a series of impulses. of selected polarities is placed upon the control-1 line circuit. The apparatus at the control oflice. and at a field station is. operated through a cycle of operation for each series, irrespective of the character of the impulses of the series, while the character of the impulses of each series determines the. particular station. selected for that. cycle'andfthe controls trans mitted. to that selected station.

For the transmission of indications, a series otzimpulses. is. placed upon the indication line circuit; which impulses set up distinctive conditions. by reason of-their presencev or absence on the. steps of each: cycle, these steps being marked offiby impulses'placed upon the control line cir Guilt.

the'presence. or absence of trains on various systom,.but,some.' are located near or adjacent 7 With such an arrangement, whenever a cycle oioperation occurs for the transmission of indi cations alone; then the seriesof-impulses placed upon. the control line circuit for causing-the step-*by-stepoperation must b'e'of such a char acter. as; not to-select any-field'station, but to merely cause the. stepbystep operation at" that field station When" transmitting itsindications. Similarly, whenever a cycle of operation occurs for the transmission of controls alone, then there are no. impulses placed upon the indication. line circuit, thereby setting up distinctive conditions whifohforma code, and this code is not'employed by any: field'station, soas to prevent thefalse registrationoi a station whenit is not trans mitting indications. I

i with the intermediate tap (CN).

For the purpose of simplifying the illustrations and facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose in mind of making it easy to understand the principles and mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, and symbols are used to indicate connections to the terminals of batteries, or other sources of electric current, instead of showing all of the wiring connections to these terminals. Also the coding apparatuses have been shown conventionally by dotted rectangles.

The symbols and are employed to indicate the positive and negative terminals 'respectively of suitable batteries, or other sources of direct current; and the circuits with which these symbols are used, always have current fiowing in the same direction. The symbol (13+) and (B) indicate connections to the opposite terminals of a suitable battery, or other direct current source which has a central or intermediate tap designated (CN) and the circuits with which these symbols are used, may have current flowing in one direction or the other depending upon the particular terminal used in combination Vfhen alter nating current is used in place of direct current, the particular symbol employed represent the relative instantaneous polarities.

Communication system generalZy.-The general plan of organization of a system contemplated upon which the present invention is superimposed may be best understood by referring to Pat. No. 2,082,544. It is to be understood, of course, that the system may be extended so as to provide as many field stations as necessary to govern the territory placed under the supervision of the operator'in the control office, but for convenience in describing the present invention, only one field station has been shown in each of Figs. 1 and 2.

A control line wire l extends from the control office to the first field station, from the first field station to the second field station, and so on to the end of the system where it is connected to the control line return wire l2 which extends from the control oflice through each of the field stations. Similarly, an indication line wire I4 extends from the control office to the first field station, from the first field station to the second field station, and so on, to the end of the system where it is open ended. Associated with this indication line wire 14 is an indication line return Wire l6 which extends from the control office through the several field stations and to which the indication line is connected at that particular field station selected for the transmission of indications during a cycle of operation, as more specifically ex-- plained in Patent No. 2,082,544. Although a four wire system has been shown for convenience in illustrating one embodiment of the present invention, it is to be understood that one Common return wire may be used in place of the two return wires I2 and I6. In other words, the system may be termed a'two line circuit system which circuits may be combined in any suitable manner, such as by the provision of a single com mon return wire, thereby making a three line wire system, or by both line circuits superimposed upon two line wires by employing distinctive currents such as direct current and alternating current, or by the use of two frequencies which do not have common harmonics. Also, if desired, a two line wire system such as shown in the patent to Hail-es et al., Patent N0. 2,259,561, dated Octo-' ber 21, 1941, may be employed. Energy for the control line circuit is supplied from a control battery in the control ofiice with the particular polarity selected by pole changing contacts located on code sending relays controlled by wires PC and NC respectively (see Figs. 1 and 2A) These wires correspond respectively to wires 41 and 48 in Fig. 5 of the above mentioned patent to Judge et al., and it is illustrated in Fig. 4 of that patent how the pole changing contacts of the code sending relays control the polarity of the control line circuit. When the code sending relay connected to wire PC is energized, a positive impulse is placed on the control line circuit, but when the code sending relay connected to wire NC is energized, a negative impulse is placed upon the control line circuit. With both the code sending wires energized or deenergized the control lin circuit is maintained deenergized. Wheneverenergy is applied to the control line circuit by the code sending relays, such energization is broken up into time spaced impulses by the periodic operation of the stepping apparatus.

The indication line circuit includes message relays in its two branches in the control oflice and includes pulsing contacts in the corresponding branches at each field station. As corresponding branches are selected at the control ofiice and at each field station when the control line circuit is energized closing front contacts on the repeating relays for the control line circuit, andas corresponding branches ar v connected inseries during the deenergized condition of the control line circuit as repeated at the control oflice and at each field station by the closure of suitable back contacts, these two branches of the indication line circuit at the control oflice and at each field station maybe conveniently termed front and back branches. In the control ofiice, a message relay is included in the back branch, and similarly, a message relay is included in the front branch of the indication circuit, all as clearly illustrated in Figs. 4 and 6 of the Judge et al. patent above referred to.

Structure of Fig. 1.Referr ing'to Fig. 1 of the drawings the coding apparatus employed in the oflice has been shown by dotted rectangles desig: nated Oflice coding apparatus. The switch machine lev'er BSML and the starting button 68B correspond to like apparatus shown in Fig. 5 of the Judge et al. Patent No. 2,082,544; whereas, the track occupancy indicating relay BIRB, its contact 232, the indicating lamp 60S and the station relay 6ST correspond to like designated devices illustrated in Fig. 6 of this Judge et al. patent. The apparatus shown in the right-hand portion of Fig. 1 of the drawings, that is, at the field station of the system shown co-rrespondsas to the track switch GTS, the switch machine GSM,

" the switch machine control relay SWR and BWN,

The wires shown in heavy lines as well as the 'out-of-correspondence indication relay 600R, the

indicating lamp GQCL, thethermal relay'fiTE'and theq. out-of-correspondence transmitting relay GTER have been added as a. partof. the. present invention as it-is appliedv to the disclosure of the above-mentioned Hailes et. all and Judge et a1.

patents.

Operation of'Fz'g. 1 structura-Jnorderto point out how the structure which was added to the disclosures-oi the patents to Hailes et a1. and Judge et al. performs new functions, certain operations of the entire system will be described from which the new [functions and the apparatus which produces them may be readily understood. Let us assume that the operator in the office shown at the left-hand end of Fig. l of thedrawings desiresto operate the track switch BTS shown in the right-hand portion to the reverse or takesiding position and in order to do so moves the switch machine lever BSML from its right-hand position to its left-hand position and then depresses the starting push button BSB. Depression of the starting button GSB will initiate the coding apparatus into operation and will transmit a station can code consisting of current im pulses of positive and negative polarity over the control wires l and I2 to the field station illustrated at the right-hand end of Fig. 1 of the drawings. This station code call will then pick up a station relay (notill'ustrated but comprising a part of the illustrated field coding apparatus) which will connect the various control relays at that field station to the field codingapparatus through contacts of stepping relays. The second part of the code will have impulses olfpositive and negative polarities depending upon the position assumed by the switch control lever BSML which second part will be different than the code portion that would have been trans mitted if the switch machine control lever had not been moved, this by reason of the fact that the circuit including the wire NC has been closed and the circuit including the wire PC has been open by this operation of the switch control lever GSML.

The code that is transmitted to the field station (lever SSML to the left) is such as to momentarily complete an energizing circuit for the reverse switch control relay BWR. The picking up of this relay G'WR will, at its back contact 350,

open the stick circuit for the normal switch control relay GWN and will at its front contact 350 close a stick circuit for the relay GWR including the back contact of the normal switch control relay GWN. Also, the picking up of the relay GWR and the dropping of the relay BWN will close a switch machine reversing circuit including back contact 352 of the relay GWN and (front contact 353 of the relay BWR. The moment that the switch machine is energized and unlocked the switch machine repeater relay BWP is deenergized and its neutral contact finger moves-to retracted position. Two, circuits are, therefore, closed for-the'heating element of the time element device STE; This time element device GTE may be of any suitable construction but a illustrated comprises a relay of the thermal bimetallic type including a heating coil which if heated will cause I the closure of its contacts 354 after the lapse of aces-s57 the. thermal .relayi'lZEt and, through back? contact 358" of the out-of-correspondence transmitting stick relayGTER, and (2') a similar circuit which, however, includes back-contact 355 of the relay BWN and backcontact 359 of the switch repeating relay BWP. Under normal conditions the switch machine GSM will be operated to its new or reverse position before the contacts 354 of the thermal relay GTE close. If we assume this to be the case, it will be seen that both of the circuits above mentioned will be opened. The first ond mentioned circuit will beopened by the open ing orf back contact 359 of the switch repeating relay BWP. Since both of these circuits havenow been opened the thermal time element relay STE may'again, cool and will, therefore, not have performed the function of picking up the out-of-correspondence transmitting relay STER. 3

Let us now assume that the track switch GTS was attempted to be operated as before, but was jammed as by a lump ofcoal which did not allow the switch machine GSM to complete its operating stroke. Under this assumed condition the switch machine repeater relay SWP will remain in its deenergized position with its polar contact 351 in its right-hand position. The assumed condition is with the relays GWR and GWN energized and deenergized respectively, and with the track switch jammed. Under this conditionboth of the energizing circuits hereto-fore traced for the thermaltime element relay GTE will remain closed. After the lapse of a predetermined period of time the contacts 354 of the thermal relay GTE will close, thereby closing a pick-up circuit for the out-of-correspon'dence trans mitting relay BTER which may be readily traced and which includes both of the two circuits for the time element relay BTE heretofore traced and further including the contact 354 of this relay STE. The completion of this circuit causes the relay GTER to be picked up, which relay is then stuck' up through two stick circuits for the relay BTER each including the stick contact 358 of this relay GTER, one of which stick circuits includes the right-hand polar contact 351 of relay BWP throughfront contact 356 of relay BWR and the back contact 355 of relay 5WN; whereas, the other stick circuit includes the back con tact 359 of the relaY-BWP and the back contact 355 of the relay BWN. The picking-up of the relay BTER momentarily breaks the stick circuit for the change relay SCI-I at the back and front contacts 360 of the'relay BTER, since this momentary opening of the contact 350 occurs at a time when the shunt around this contact, and including the contacts 35I and 352 of the relay GWP and front contacts 363'and- 364 of the re-- lay BWR and GWN respectively, is open. The change relay SCH will be actually momentarily deenergized and will assume its retnacted position until a code has been transmitted from that field station. The dropping of the change relay 60H by reason of the closure of its back contact I54 will initiate the communicating system into operation, assuming that the system was at rest. With the front contact 366 of the relay GTER closedan out-of-correspondence code portion preceded with a station selecting code-portion will be transmitted to the central office over the indication wires I4 and Hi. The station selecting portion of this code will result in the energization of the station selecting relay 6ST in the ofi'lce, all in a manner as clearly described in the patent to Judge et al., No. 2,082,544. With the station selecting relay 6ST now momentarily energized and with its front contacts 23! and 363 closed the ou't-of-correspondence.relay BOCR is operated to its right-hand position by reason of the fact that front contact 366 of the relay BTER at the field station'was then closed at the time a code was transmitted, resulting in the transmission of the proper code. The indicationrelay EIRB will also be operated to its right-hand circuit closed position'or to its left-hand circuit open position to either light the OS lamp 608, or extinguish the same depending upon whether the detector track relay GTR is then deenergized or energized. The operation of the out-of-correspondence relay 600R to its right-hand position will by the closure of its polar contact 369 cause illumination of theout-of-correspondence lamp 6OCL. This will inform the operator that the track switch 6TS does not assume its takesiding position which the switch machine control lever SSML, which now assumes its left-hand position, calls for.

Let us now assume that the operator desires to return his switch to the normal position on the theory that there is no particular advantage in having, a track switch assume an intermediate position and that the operator to do so now returns his switch control lever BSML to its normal right-hand position. Let us also assume that he depresses the start push button 683 and that this results in the immediate transmission of a code to the field station which will cause the normal switch control relay 6WN to be energized. The normal relay 'GWN will, of course, assume its energized position before the reverse switch control relay BWR assumes its deenergized position,

because it is the picking up of the relay 6WN that by the opening of its back contact results in the dropping of the relay 6WR. During this transition the back contacts 355 and 356 of the relays 6WN and 6WR, respectively, are both open, thereby causing a momentary break in the stick circuit for the out-of-correspondence transmitting relay BTER, thereby causing this relay BTER to again return to its normal deenergized position. Since during this transition, nam'ely when the relay BWR and GWN both assume their deenergized position, the switch repeater relay 6WP is still assuming its deenergized position and has its front contact 36l open, the contact 360 of the relay B'IER. is shunted and moves from its front to its back position. The dropping of contact 360 of relay ETER. while unshunted, of course, results in the deenergization and dropping of the change relay SCI-I (this change relay having in the meantime been picked up by suitable means contained in the field coding apparatus) thereby again initiating the coding apparatus into operation at a time when the front contact 366 of the relay STER isopen. The code now transmitted to the central oflice will be of a character (contact 366 being open) to operate the out-of-correspondence relay 60GB back to its normal left-hand position if it is not already assuming that position. In practice, however, the relay GOCR would have already assumed the left-hand position, because of closure of a local circuit which was closed by the operation of the switch machine lever GSML to its right-hand position for the purpose of returning the track switch to its normal position. This local circuit is closed when the switch machine IeVer GSML assumes its middle position and may be traced from the terminal through the contact 310 of the lever 6SML and through back contact 368 of the station selecting relay 6ST. In other words, every operation of the switch machine control lever BSML to a new active position will result in the deenergization of the out-of-correspondence lamp BOCL if then lighted. Furthermore, if an indication is sent in from the particular field station at which the relay STER- is located and this relay 6TER. is then in its retracted position, a code will be transmitted to the office which will result in the operation of the out-o-f-correspondence relay 600R. to its lefthand position, resulting in the indicating lamp 6OCL being extinguished.

It has just been assumed that the operator after making an attempt to operatethe switch GTS to its reverse position, which was unsuccess ful, and then returned his lever to the normal position. It was observed that due to the fact that the switch control relay 6WN picked up before the switch control relay 6WR dropped that the stick circuits for the relay GTER were momentarily broken, to cause this relay BTER to assume its deenergized position. Let us now assume that the track switch 6T8 could also not be returned to its normal position. If this is the case the thermal relay GTE .will again be energized through a circuit including back contact 356 of the relay 6WR and back contact 359 of the relay 6WP and if this were to prevail for said predetermined period of time the thermal relay B'I'E would close its front contact 354 thereby again picking up the out-of-correspondence transmitting relay BTER. This would, of course. result in the dropping of the change relay BCH and in th transmission of an out-of-correspondence code to the central office due to the fact that front contact 366 of the cut-of-corresponda ence relay 6TER is then closed. This code would, of course, again illuminate the out-of-correspondence lamp 6OCL and would inform the operator that the track switchGTS is out of correspondence with the switch machine control lever GSML. It is readily seen that closure of back contact 359 of the switch repeating relay 6WP manifests thatthe switch machine is unlocked. It is also readily seen that the contacts 355, 356, and 35'! in combination constitute outof-correspondence contacts to establish a circuit which is closed when non-correspondence exists. It is also readily seen that the contacts 363, 364 and 362 of the relays 6WR, BWN and 6WP constitute in combination the correspondence contacts which close branch circuits only when correspondence between these switch control relays and switch repeater relays exists and that these branch circuits during correspondence conditions shunt the contact 360 of theout-of-correspondence transmitting relay G'I'ER.

Structure of Fig. 2.-The switch control lever 8SML, signal control lever 4- 5SGL, starting push button 883 and the office coding apparatus correspond to like apparatus shown in Fig. 1 of the Hailes et al. Patent No. 2,229,736; Whereas, the station selecting relay 8ST its associated contact 23 l the indication relay'BIRB, its associated contact-232 and the track occupancy lamp 808 correspond to similar, devices of Fig. 6 of the Judge et a1. Patent No. 2,082,544. All of the apparatus and circuits illustrated in light lines in Fig. 2B of the drawings except the change relay H correspond to like devices shown in Fig. 3B of the Hailes et a1. Patent No. 2,229,736,; the

chang relay 80H and its associated contacts 22 and circuitswhich are superimposed upon the structure of the Hailes etal. and Judge et al. patents to constitute the present invention;

Referring to Fig. 2B of the drawings, this figure of the drawings illustrates a short section of track including the end of a passing siding connected to the main track by a track switch 8TS. -This track switch is operable by a switch machine 83M and has associated therewith eastbound starting signals 4A and 4B and west-bound entering signals A and 5B. These signals comprise part of an absolute-permissive-block signalling system including a directional stick relay AS, home-distant relays 1H and 5AI-I and associated trackrelays (TR and-8TB. The switch machine BSM which operates the track switch 8TS is controlled by switch control relays BWR and 8WN; whereas, the signals 4A, 4B, 5A and 5B arecontrolled by signal relays 4 AG, ABG, 5AG, 5BG, which signal relays arein turn controlled by code controlled signal control relays 4G2, 5GZ and 4-53 and by correspondence relays BRCR and SNCR. As in the Fig. l structure the apparatus includes a thermal time element relay 8TE and an out-of-correspondence transmitting relay 8TER. The change relay 8Cl-I corresponds to the change relay CH shown in Fig. 3 of the Judge et al. patent above referred to.

Operation of Fig. 2 structure.-Before going into the actual operation of the system illustrated in Figs. 2A and 2B let us first observe that the contact 36b of the out-of-correspondence relay BTER is normally shunted by the following shunting circuit: beginning at the left-hand terminal of the contact 360, front contact 380 of the switch control relay -8WN, polar contact 38! of switch repeating relay 8WP, back contact 382 of the signal control relay 462, back vcontact 384 of the signal relay 4AG, back contact 385 of the signal relay 4BG, back contact 386 of the signal control relay 5G2 and back contacts 381 and 388 of the signal relays 5AG and 5BG, respectively, and then to the opposite side of the contact 360. By the careful study of these contacts together with .the contacts 390 of switch control relay 8WR,

39! of signal relay 5AG, and 392 of signal relay AAG, it will be seen that any out-of-correspondence condition between the switch control relay and signal control relays and the switch repeater relay and signal relays which they control'will cause this shunting circuit to be opened; In otherwords, these contacts perform the same functions for a plurality of devices that the contacts 353, 354, 362, and 36| for the single track switch of the Fig. 1 structure perform.

Let us now assume that the operator in th central ofiice wishes to clear the signal 4A and in order to do so he moves his signal control lever 4-5SGL into its right-hand dotted position. This movement of the signal lever causes mome'ntary closure of the circuit starting at the terminal contact 394 of the signal control lever 4-5SGL, back contact 368 of the station relay EST to the winding of the out-of-correspondencerelay BOCR. The operator upon depressing his starting button 8SB will initiate the system into operation and will cause a code to be transmitted to the field station shown in Fig. 2B. The first portion of this code will select that field station and the second portion of this code will, among other things, cause energization of'the' signalcontrol relay "4GZ; The moment that this signal control relay is energized, it"will be stuck up through a stick circuit starting from the terminal (-1-) of a suitable battery through front contact 335 of track relay BTR, back con tact 396 of the signal stop relay 4-53 and through stick contact :391. With the signal con-. trol relay 4GZ now energized a circuit for the heating coil'of the thermal relay BTE, which may be traced as follows is closed: beginning at the terminal of a' suitable source of current, front contact 400- of' the signal" control: relay 4GZ, back contact Mil of the signal/relay 4A6, back contact AOZof the signal relay 413G, heat--. ing coil of the thermal relay 8TE and through back contact 358 of the"out-.of-correspondence transmitting relay.8 TER tothe other terminal minus of the same. source .of' current. 'If there is no train directly ahead of the signal-4A, the circuit for the signal relay '4AG and in cluding the front contact 454 of the relay AGZ, the front contact 4H5 of the switch repeating cor,-. respondence relay 8NCR and the front contact 305 of the home distant relay 4H willtbe closed. The signal relay 4AG willrunder the assumed condition be immediately picked up and will directly ahead of the'signal 4A but beyond the detector track circuit including track relay 8TB; and that the home relay 4H is for this reason deenergized, it will be seen that the back contact Mil of .the signal relay 4AG' remains closed and that'the thermal relay 8TE is energized. tion of the thermal-relay BTE is continued-for a predetermined time sufiicient to allow the particular signal orthe switch machine to have completedits operation, this thermal relay STE will close its contact- 354 and in so doing will complete a pick-up circuit for the out-of-correspondence transmitting relay 8TER. The completion of this pick-up circuit will, of course, cause the relay 8TER to assumeitsenergized position thereby closing its stick circuit moving its contact 360 from its back point to its front point .and since this contact 360 is no longer shunted, the circuit through the front'contact 382 of the relay 462 being open atfront contacts 382 and 3850f the relays AAG and -4BG, respectively, the stick circuit for change relay 8CH is broken; that is, with contact 360 of the relay 8TER unshunted, it movement from its back point to its front point will cause momencorrespondence. relay 800R to bev operated to its left-hand polar position to light the out-of-correspondence lamp 8OCL.- This'will, of cQLu'se, inform the operator that his movement of the signal lever 4'5SGL has resulted: in-an out-oh correspondence condition as between the control: relay which this lever controls ;a nd the If this'conditionof energizasignal relay which sihh signal control relay controls, and the operator will be informed that his signal 4A did not clear.

In a similar manner the failure of the switch machine or some other signal to operate in time in response to a change in the position of its control lever will cause the out-of-correspondence lamp 8OCL to be illuminated to inform the operator of this fact.

The applicant has thus devised a remote control and indication system of the code communication type in which the positions assumed by the control levers, when interpreted in the light of the conditionof an out-of-correspondence indicator, may be ascertained without transmitting by code either the position assumed by the device controlled by such lever or the fact that it is in correspondence with such lever. That is an indication, namely an out-of-correspondence indication, is only transmitted when an abnormal and unusual condition exists at the field station. By this construction very few indications need be transmitted by the code type communication system as a result of which a larger number of control codes may be transmitted without overloading the system. It is desired to be understood, however, that the particular system shown and described does not exhaust all forms the invention may take, and that the particular form shown has been selected to facilitate illustration and description of the invention, and it should further be understood that various changes, additions and alterations may be made to adapt the invention to the particular problems encountered in practicing the same all without departing from the spirit of the invention except as demanded by the scope of the appended claims.

What I claim as new is:

1. In a centralized trafiic controlling system for railroads, in combination with a section'of railway track at a field station including a track switch, a switch machine for operating said track switch, a detector track circuit associated with said track switch, a signal for governing trafilc over said track switch, two electro-responsive devices one for controlling said switch machine and the other for controlling said signal, a switch control lever and a signal control lever at a control office, a correspondence indicator and a track indicator at said oifice, a time element device at said field station controlled by a circuit which is closed only if said track switch or said signal is out of correspondence with its respective electroresponsive device and rendered active a time after closure of its circuit which is greater than the time required for said switch machine or said signal to be operated, and a code type communicating system connecting said office and said field station for controlling said electro-responsive devices in accordance with the positions assumed by their respective control levers and for controlling said non-correspondence indicator and said track indicator respectively in accordance with whether said time element device is active or inactive and whether said detector track circuit is occupied or unoccupied, whereby if the non-correspondence indicator is active and said track indicator is inactive such condition may be taken as an indication that another track circuit capable of putting said signal to stop is occupied.

2. In a centralized traific controlling system for railroads, in combination with a section of railwaytrack at a field station including a track switch, a switch machine for operating said track switch, a detector track circuit associated with said track switch, a signal for governing trafiic over said track switch, two electro-responsive devices one for controlling said switch machine and the other for controlling said signal, a switch control lever and a signal control lever at a local oifice, a normally inactive non-correspondence indicator and a track indicator at said ofic'e, a time element device controlled by a circuit which is closed only if said track switch or said signal is out of correspondence with its respective electroresponsive device and rendered active a time after closure of its circuit which is greater than the time required for said switch machine or said signal to be operated, and a code type communicating system connecting said office and said field station for controlling said electro-responsive devices in accordance with the positions assumed i by their respective control levers and for controlling said non-correspondence indicator and said track indicator respectively in accordance with whether said time element device is active ,or

inactive and whether said detector track circuit is occupied or unoccupied, and means responsive to the -movement of either of said levers to another position for restoring said non-correspondence indicator to normal, whereby if the non-correspondence indicator is active and said track indicator is inactive such condition may be taken as an indication that another track circuit capable of putting said signal to stop is occupied.

3. In a centralized traflic, controlling system for railroads, in combination with a section of railwaytrack at a field station including a track switch, a switch machine for operating said track switch, a detector track circuit associated with said track switch, a plurality of signals for governing trafi'ic over said track switch, a plurality of electro-responsiVe devices one for controlling said switch machine, and one for each direction of trailic controlled by said signals, a switch control lever and a signal control lever at a local office, a non-correspondence indicator and a track indicator at said office, a time element device controlled by a circuit which is closed only if said track switch or any one of said signals is out' of correspondence with its respective electroresponsive device and rendered active a time after closure of its circuit which is greater than the time required for said switch machine or any one of said signals to be operated, and a code type communicating system connecting said ofiice, and field station for controlling said electro-responsive devices in accordance with the positions assumed by their respective control levers and for controlling said non-correspondence indicator and said track indicator respectively in accordance with whether said time element device is active or inactive and whether said detector track circuit is occupied or unoccupied, whereby if the non-correspondence indicator is active and said track indicator is inactive such condition may be taken as an indication that another track circuit capable of putting a signal to stop is occupied.

4. In a centralized traflic controlling system of the code type, in combination with an office and i a field station, a code communicating system connecting said office and field station including a change relay normally energized by a stick circuit and located at said field station for when tem', an *out-of-correspondence relay at said field station energized after a period of delay in response to actuation of said electro-responsive means out of correspondence with said traffic controlling device, a contact controlled by said out-of-correspondence relay and included in said stick circuit for momentarily opening said stick circuit to drop said change relay in response to a change in the position assumed .by said out-ofdeenergized initiating. the transmission of a code i from said field station, a plurality of trafiic controlling devices at said field station, an electroresponsive means at said field station for each of said traific controlling devices to control the same,

a lever in said omce for controlling said electro- I responsive means through the mediumof said communicating system, an out-of-correspondence relay at said fieldstation energized after a'period of delay in response to actuation of any one of said electro-responsive means out of correspondence with its traffic controlling device, a contact controlled by said out-of-correspondence relay and included in said stick circuit for momentarily opening said stick circuit to drop said relay in response to a change in the position assumed I by said out-'of-correspondence relay, and a shunting circuit for bridgingsaid contact and closed only if all ofsaid electro-responsive means and their associated trafiic controlling devices assume corresponding positions. I

6. In a centralized traffic control and indication system of the code type; in combination with a stretch of track; a traffic controlling device for from aicontrol oflice, maflually operable means at thecontrol office having normal and reverse positions, electro-responsive means at the field station-having normal and reverse. positions, code communication means foroperatingsaid electroresponsive means "in correspondence with the respective .normal and reverse positions of said manuallyoperable means,'circuit means :at the field station responsive to said electro-responsive means for causing the power operation of said track switch to a normal or a reverse position in correspondence with such electro-responsive means, an out-of-co rrespondence indicator at the control office, and codecommunication means, including time controlled means and a separate source of, energy for the time controlled means, for communicating a control from the field station toxthe control office for the energization of said indicator when. said track switch is out :of correspondence 'With said electro-respon'sive means, such communication means being efiective to communicate a control for the energizasaid stretch; a control relay for controlling said 7 -trafiic controlling device; code communicating apparatus including an office, afield station, oifice coding apparatus at said oifice and'field coding apparatus at said field station connected by line wires for transmitting control codes from said office to said field station and transmitting indication codes from said field station to said 'oflice, such apparatus being normally at rest; an out-ofcorrespondence relay which if energized initiates said code communication apparatus and transmits an out-of-correspondence code to said ofiice; a time. element device, having an energizing circuit closed so long as said trafiic controlling ,device and said control relay assume out-of-correspondence conditions and rendered active if said energizing circuit is closed for more than a predetermined period of time and restored to normal if said energizing circuit is broken before the" lapse of said predetermined time, for when active energizing said out-of-correspondence relay; means effective when said out-of-correspondence relay assumes its energized position and initiates said apparatus for transmitting an out-of-correspondence code to said office; and an out-of-correspondence indicator at said office rendered active in response to' the transmission of an outof-correspondence code from said'field station to said office. l

7.'In a coded centralized traffic control system for-railroads for governing a power track switch at onset a plurality of field stations each'remote temporary tion of said indicator only if-said track switch has been out of correspondencewith said electrore'spons'ive means fora period of'time longer than thatnormally required for the power operation of that'track switch whereby'to make the code communication means available during the time of temporary out-of-correspondence condi tions, for-other communication use, and to'prevent unnecessary use of the code communication means.

*8. In acoded centralized traffic control system for. railroads for governing a power track switch atone of a plurality of field stationseach remote from a control office, manually operable means at the control'ofiice having normal and reverse positions, eleotro-responsive means at'the field station having 'normaland reverse positions, code communication means for operating said electroresponsive means in correspondence with the respective normal '1 and reverse positions of said manually operable means,'circuit means at the field station responsive to said electro-responsive means for causing the 'power operation of said track'switch't'o 'a' normal or .a reverse" positionin correspondence with such electro-responsive means, an out of-correspondence indicator at the control ofiice, code communication means for communicating'a control 'from the field stationto the' control oifice for the energization of said indicator when said'track switch is out of correspondence with said 'electro-responsive means, such communication means including a time controlleddevice "and a separate'source of energythat track'switch, whereby to make the code communicaticn means available during the time of out-of-correspondence conditions, for other communication use, and to prevent unnecessary use of the code communication means and circuit means at the control ofiice for deenergizing said indicator upon movement of said manually operable means from one operating position to the other.

9. :In a coded centralized traffic control system I sponsive means at the field station having normal reverse positions of said manually operable means, circuit means at the field station responsive to said electro-responsive means for causing the power operation of said track switchito a normal or a reverse position in correspondence with such electro-responsive means, an out-ofcorrespondence indicator at the control oflice, and code communication means for communicating a control from the field station to the control office for the energization of said indicator when said track switch is out of correspondence with said electro-responsive means, such communication means being efiective only if said track switch has been out of correspondence with said electroresponsive means for a longer than normal period of time, and such communication means being effective in response to operation of the manual means to a new position and after the expiration of said longer than normal period of time, to communicate another control to cause the deenergization of said indicator subsequent to its energization at the end of said longer than ,normal period of time.

10. In a coded centralized trafi'ic control system for railroads for governing a power track switch at a field station remote from a control office, manually operable means at the control office having normal and reverse positions, electro-responsive means at the field station having normal and reverse positions, code communication means for operating said 'electro-responsive means in correspondence with the respective normal and reverse positions of saidmanually operable means, circuit means at the field station responsive to said electro-responsive means for causing the power operationof said track switch to a normal or a reverse position in correspondence with such electro-responsive means, an outof-correspondence,indicator at the control oifice, code communication means-for communicating a control from the field station to the control ofiice for the energization of said indicator when said track switch is out of correspondence with said electro-responsive means, such communication means being eifective to communicate a control for the energization of said indicator only 9 tem for railroads for governing the clear and stop indications of a signal at any one of a plurality of field stations remote from a control ofiice,

manually operable means at thecontrol office for said signal having distinctive stop andclear operating-positions, electro-responsive means at the field station for said signal having distinctive clear and stop positions, code communication means for operating said electro-responsive means to positions corresponding to those of said manually operable means at the control ofiicep circuit means at the field station responsive to said electro-responsive means for causing said signal to indicate clear or stop in accordance with the manner in which said electro-responsive means is conditioned, an out-of-correspondence indicator at the control oflice, and code communication means for communicating a control from the field station to the control office for the energization of said indicator when saidsignal is out of correspondence with said electroresponsive means, such means being efiective to communicate that control only if said signal has been out of correspondence with said e1ectro-, responsive means for a period of time greater than that normallyrequiredfor response of that signal to the positioning of said'electro-responsive means. I l

'12. In a coded centralized traific control system for railroads for governing the clear and stop indications of a signal at a field station remote from a control ofiice, manually operable means at the control oflice for said signal having dis-- tinctive stop and clear operating positions, electro-responsive means at thefield station for said signal having distinctive clear and stop positions, code communication means for operating said electro-responsive means to positions correspond ing to those of said manually operable means at the control ofiice, circuitmeans at the field station responsive to said electro-responsive means if said track switch has been out of correspondence with said electro-responsive means for a longer than normal period of time, and such communication means beingefiective to communicate another control to cause the deenergization of said indicator subsequent to its energization at the end of said abnormal period, upon movement of said manual means to a new position and subsequent to the expiration of said longer than normal period of time, and circuit for causing said signal to indicate clear or stop in accordance with the manner in which said electro-responsive means is conditioned, an out-ofcorrespondence indicator at the control office,

code communication means for communicating a control from the field station to the control office for the energization of said indicator when said signal is out of correspondence withsaid electro-responsive means, such means being effective to communicate that control only if said signal has been out of correspondence with said electro-responsive .means for a period of time greater than that normally required for the response of such signal, and such communication to cause the deenergization of said indicator subsequent to its energization at the end of 'such abnormal period; I

SEDGWICK N. WIGHT. 

